The current energy policies around the world have encouraged the development of renewable, clean and sustainable chemicals in an effort to reduce greenhouse emissions. The conversion of sustainable biomass for the production of energy and high value chemicals has been proposed as an enabling technology and received a great deal of interest for decades. From a technical perspective, chemicals extracted from biomass require fewer steps, are more amenable to aqueous processing, and generate less waste than their oil-based counterparts. Thereby, various biomass feed stocks such as cellulosic plants, algae, triglyceride plants, and rubber plants have been suggested as precursors to produce biochemicals and biofuels (diesel, gasoline or ethanol). However, to the best of our knowledge, none of these technologies offer an efficient process for the production of liquefied petroleum gas (LPG) from biomass.
LPG is composed of low-C hydrocarbons (e.g., lightweight C3 and C4 compounds) and is a versatile fuel that can be used for heating, cooking, and power generation. Furthermore, LPG storage and transportation technology is mature and is prevalent amongst industrial, commercial, and consumer processes. Using LPG creates significantly lower harmful emissions, such as carbon dioxide (CO2), than using gasoline or diesel. Therefore, LPG obtained from sustainable biomass feed stocks can provide clean energy.
Current proposed technologies for the production of LPG from biomass involves using synthesis gas (carbon monoxide (CO)+hydrogen (H2)) as an intermediate, which can be obtained by the gasification of cellulosic biomass (i.e. woody chips and agricultural wastes). The synthesis gas is then converted to LPG using catalytic processes at a high temperature (>700° C.) and pressure (up to 20 bar). The products and byproducts obtained from the catalytic process require multiple separation steps, which increase the capital and operation costs of the LPG production. On the other hand, biomass derivatives (e.g. platform chemical mixture) can be converted into high value chemicals and hydrocarbon fuels by catalytic routes. An example of high-value biochemical production includes aromatic hydrocarbons (benzene, toluene, xylenes (BTX), etc.), which could be produced from solid biomass via fast pyrolysis techniques or thermal deoxygenation. However, to the best of our knowledge, production of biomass-derived LPG (bio-LPG) and bioaromatics requires high operating temperatures and complex separation processes due to the low product yield.